crypto_exchange

gRPC service that fetches currency exchange rates from exchangerate-api.com and converts amounts between currencies. Rates are cached in memory using the API's own update schedule as TTL, so you're not paying for the same request twice.

Requirements

• Docker + Docker Compose
• Make
• Postman or grpcurl (for testing)

Getting started

Add your API key to .env:

EXCHANGE_RATE_HOST=https://v6.exchangerate-api.com/v6
EXCHANGE_RATE_TOKEN=your_key_here

Then start the server:

make up

Server listens on :50051.

Make commands

make up            # build image and start container
make down          # stop container

make proto         # regenerate Go code from .proto files
make buf-lint      # lint proto files
make buf-breaking  # check for breaking changes vs main

make build         # compile binary
make lint          # run golangci-lint
make tidy          # go mod tidy

API

Two RPCs defined in proto/exchange/v1/exchange.proto.

GetExchangeRate — get the rate between two currencies

// request
{ "from_currency": "EUR", "to_currency": "GBP" }

// response
{ "from_currency": "EUR", "to_currency": "GBP", "rate": 0.8652 }

ConvertCurrency — convert an amount

// request
{ "from_currency": "EUR", "to_currency": "GBP", "amount": 100 }

// response
{
  "from_currency": "EUR",
  "to_currency": "GBP",
  "amount": 100,
  "converted_amount": 86.52,
  "rate": 0.8652
}

Currency codes must be valid ISO 4217 (3 uppercase letters). Anything else gets rejected before hitting the API.